Inter-layer texture coding with adaptive transform and multiple inter-layer motion candidates

ABSTRACT

Methods of adaptive transform type based on transform unit (TU) size for enhancement layer (EL) coding and multiple motion candidates for EL coding based on corresponding base layer (BL) video data are provided. One method selects a transform type from multiple allowable transform types based on the TU size and applies the selected transform type to the transform units of the inter-layer prediction processed data. Another method derives multiple motion candidates for the EL video data coded in Merge mode or Inter mode based on motion information associated with the corresponding BL video data.

RELATED APPLICATIONS

This Application is a Division of U.S. application Ser. No. 14/442,925,filed May 14, 2015, entitled “INTER-LAYER TEXTURE CODING WITH ADAPTIVETRANSFORM AND MULTIPLE INTER-LAYER MOTION CANDIDATES”, which is anational stage filing under 35 U.S.C. 371 of International PatentApplication Serial No. PCT/CN2013/086151, filed Oct. 29, 2013, whichclaims the benefit of U.S. Application Ser. No. 61/726,837, filed Nov.15, 2012, each of which is hereby incorporated by reference in itsentirety.

FIELD OF THE INVENTION

The present invention relates to scalable video coding. In particular,the present invention relates to inter-layer texture codingincorporating adaptive transform or multiple inter-layer motioncandidates.

BACKGROUND AND RELATED ART

Compressed digital video has been widely used in various applicationssuch as video streaming over digital networks and video transmissionover digital channels. Very often, a single video content may bedelivered over networks with different characteristics. For example, alive sport event may be carried in a high-bandwidth streaming formatover broadband networks for premium video service. In such applications,the compressed video usually preserves high resolution and high qualityso that the video content is suited for high-definition devices such asan HDTV or a high resolution LCD display. The same content may also becarried through cellular data network so that the content can be watchon a portable device such as a smart phone or a network-connectedportable media device. In such applications, due to the networkbandwidth concerns as well as the typical low-resolution display on thesmart phone or portable devices, the video content usually is compressedinto lower resolution and lower bitrates. Therefore, for differentnetwork environment and for different applications, the video resolutionand video quality requirements are quite different. Even for the sametype of network, users may experience different available bandwidths dueto different network infrastructure and network traffic condition.Therefore, a user may desire to receive the video at higher quality whenthe available bandwidth is high and receive a lower-quality, but smooth,video when the network congestion occurs. In another scenario, ahigh-end media player can handle high-resolution and high bitratecompressed video while a low-cost media player is only capable ofhandling low-resolution and low bitrate compressed video due to limitedcomputational resources. Accordingly, it is desirable to construct thecompressed video in a scalable manner so that videos at differentspatial-temporal resolution and/or quality can be derived from the samecompressed bitstream.

The joint video team (JVT) of ISO/IEC MPEG and ITU-T VCEG standardized aScalable Video Coding (SVC) extension of the H.264/AVC standard. AnH.264/AVC SVC bitstream can contain video information from lowframe-rate, low resolution, and low quality to high frame rate, highdefinition, and high quality. This single bitstream can be adapted tovarious applications and displayed on devices with differentconfigurations. Accordingly, H.264/AVC SVC is suitable for various videoapplications such as video broadcasting, video streaming, and videosurveillance to adapt to network infrastructure, traffic condition, userpreference, and etc.

In SVC, three types of scalabilities, i.e., temporal scalability,spatial scalability, and quality scalability, are provided. SVC usesmulti-layer coding structure to realize the three dimensions ofscalability. A main goal of SVC is to generate one scalable bitstreamthat can be easily and rapidly adapted to the bit-rate requirementassociated with various transmission channels, diverse displaycapabilities, and different computational resources without trans-codingor re-encoding. An important feature of the SVC design is that thescalability is provided at a bitstream level. In other words, bitstreamsfor deriving video with a reduced spatial and/or temporal resolution canbe simply obtained by extracting Network Abstraction Layer (NAL) units(or network packets) from a scalable bitstream that are required fordecoding the intended video. NAL units for quality refinement can beadditionally truncated in order to reduce the bit-rate and theassociated video quality.

In SVC, spatial scalability is supported based on the pyramid codingscheme as shown in FIG. 1. In a SVC system with spatial scalability, thevideo sequence is first down-sampled to obtain smaller pictures atdifferent spatial resolutions (layers). For example, picture 110 at theoriginal resolution can be processed by spatial decimation 120 to obtainresolution-reduced picture 111. The resolution-reduced picture 111 canbe further processed by spatial decimation 121 to obtain furtherresolution-reduced picture 112 as shown in FIG. 1. In addition to dyadicspatial resolution, where the spatial resolution is reduced to half ineach level, SVC also supports arbitrary resolution ratios, which iscalled extended spatial scalability (ESS). The SVC system in FIG. 1illustrates an example of spatial scalable system with three layers,where layer 0 corresponds to the pictures with lowest spatial resolutionand layer 2 corresponds to the pictures with the highest resolution. Thelayer-0 pictures are coded without reference to other layers, i.e.,single-layer coding. For example, the lowest layer picture 112 is codedusing motion-compensated and Intra prediction 130.

The motion-compensated and Intra prediction 130 will generate syntaxelements as well as coding related information such as motioninformation for further entropy coding 140. FIG. 1 actually illustratesa combined SVC system that provides spatial scalability as well asquality scalability (also called SNR scalability). The system may alsoprovide temporal scalability, which is not explicitly shown. For eachsingle-layer coding, the residual coding errors can be refined using SNRenhancement layer coding 150. The SNR enhancement layer in FIG. 1 mayprovide multiple quality levels (quality scalability). Each supportedresolution layer can be coded by respective single-layermotion-compensated and Intra prediction like a non-scalable codingsystem. Each higher spatial layer may also be coded using inter-layercoding based on one or more lower spatial layers. For example, layer 1video can be adaptively coded using inter-layer prediction based onlayer 0 video or a single-layer coding on a macroblock by macroblockbasis or other block unit. Similarly, layer 2 video can be adaptivelycoded using inter-layer prediction based on reconstructed layer 1 videoor a single-layer coding. As shown in FIG. 1, layer-1 pictures 111 canbe coded by motion-compensated and Intra prediction 131, base layerentropy coding 141 and SNR enhancement layer coding 151. As shown inFIG. 1, the reconstructed BL video data is also utilized bymotion-compensated and Intra prediction 131, where a coding block inspatial layer 1 may use the reconstructed BL video data as an additionalIntra prediction data (i.e., no motion compensation is involved).Similarly, layer-2 pictures 110 can be coded by motion-compensated andIntra prediction 132, base layer entropy coding 142 and SNR enhancementlayer coding 152. The BL bitstreams and SNR enhancement layer bitstreamsfrom all spatial layers are multiplexed by multiplexer 160 to generate ascalable bitstream. The coding efficiency can be improved due tointer-layer coding. Furthermore, the information required to codespatial layer 1 may depend on reconstructed layer 0 (inter-layerprediction). A higher layer in an SVC system is referred as anenhancement layer. The H.264 SVC provides three types of inter-layerprediction tools: inter-layer motion prediction, inter-layer Intraprediction, and inter-layer residual prediction.

In SVC, the enhancement layer (EL) can reuse the motion information inthe base layer (BL) to reduce the inter-layer motion data redundancy.For example, the EL macroblock coding may use a flag, such asbase_mode_flag before mb_type is determined to indicate whether the ELmotion information is directly derived from the BL. If base_mode_flag isequal to 1, the partitioning data of the EL macroblock along with theassociated reference indexes and motion vectors are derived from thecorresponding data of the collocated 8×8 block in the BL. The referencepicture index of the BL is directly used in the EL. The motion vectorsof the EL are scaled from the data associated with the BL. Besides, thescaled BL motion vector can be used as an additional motion vectorpredictor for the EL.

Inter-layer residual prediction uses the up-sampled BL residualinformation to reduce the information required for coding the ELresiduals. The collocated residual of the BL can be block-wiseup-sampled using a bilinear filter and can be used as prediction for theresidual of a corresponding macroblock in the EL. The up-sampling of thereference layer residual is done on transform block basis in order toensure that no filtering is applied across transform block boundaries.

Similar to inter-layer residual prediction, the inter-layer Intraprediction reduces the redundant texture information of the EL. Theprediction in the EL is generated by block-wise up-sampling thecollocated BL reconstruction signal. In the inter-layer Intra prediction(ILIP, or so called inter-layer texture prediction) up-samplingprocedure, 4-tap and 2-tap FIR filters are applied for luma and chromacomponents, respectively. Different from inter-layer residualprediction, filtering for the inter-layer Intra prediction is alwaysperformed across sub-block boundaries. For decoding simplicity,inter-layer Intra prediction can be applied only to the intra-codedmacroblocks in the BL.

As shown in FIG. 1, reconstructed video at a lower layer is used forcoding by a higher layer. The lower layer video corresponds to a lowerspatial or temporal resolution, or lower quality (i.e., lower SNR). Whenthe lower spatial resolution video in a lower layer is used by a higherlayer coding, the lower spatial resolution video usually is up-sampledto match the spatial resolution of the higher layer. The up-samplingprocess artificially increases the spatial resolution. However, it alsointroduces undesirable artifacts. It is desirable to develop newtechniques to use reconstructed video from a lower layer to improve theinter-layer coding efficiency.

BRIEF SUMMARY OF THE INVENTION

A method and apparatus of inter-layer prediction for scalable videocoding are disclosed, wherein the video data is configured into a BaseLayer (BL) and an Enhancement Layer (EL) and wherein EL video data hashigher spatial resolution or better video quality than BL video data.Embodiments according to the present invention receive input dataassociated with the EL video data, wherein the EL video data ispartitioned into TUs (transform units) and each TU has a TU (transformunit) size. A first type transform/inverse transform or a second typetransform/inverse transform is then applied to the input datacorresponding to the current TU of the EL video data depending on thecurrent TU size. The input data associated with the EL video datacorresponds to inter-layer texture prediction processed video data to becoded or coded inter-layer texture prediction processed video data to bedecoded. The first type transform/inverse transform can be either thediscrete sine transform (DST)/inverse DST or the discrete cosinetransform (DCT)/inverse DCT. The second type transform/inverse transformcan also be selected from the DST/inverse DST and the DCT/inverse DCT,and the second type transform/inverse transform is different from thefirst type transform/inverse transform. In one embodiment, the firsttype transform/inverse transform is used if the current TU size is equalto a pre-defined size. In another embodiment, the second typetransform/inverse transform is used if the current TU size is greaterthan a pre-defined size. The pre-defined size can be 4×4.

In other embodiments of the present invention, input data associatedwith a current EL block of the EL video data is received and acorresponding BL block in the BL is determined. Two or more inter-layercandidates are derived based on BL motion information associated withthe corresponding BL video data, wherein said two or more inter-layercandidates are added to a Merge candidate list or AMVP (advanced motionvector prediction) candidate list. A final motion vector predictor isthen derived from the Merge candidate list or the AMVP candidate listand the final motion vector predictor is used to encode or decode thecurrent EL block in the Merge mode or the Inter mode based on AMVP. Atleast one of said two or more inter-layer candidates can be derivedbased on scaled BL motion information associated with selected BL videodata in the corresponding BL block. The selected BL video data in thecorresponding BL block corresponds to at least one location of fourcorner BL pixels and four center BL pixels, wherein the four corner BLpixels and the four center BL pixels are collocated with four corner ELpixels and four center EL pixels of the current EL block respectively.The corresponding BL video data may include one or more neighboring BLblocks of the corresponding BL block and at least one of said two ormore inter-layer candidates is derived based on second scaled BL motioninformation associated with said one or more neighboring BL blocks ofthe corresponding BL block. Said one or more neighboring BL blocks ofthe corresponding BL block correspond to a bottom-left BL block, a leftBL block, an upper-right BL block, a top BL block and an upper-left BLblock. The BL motion information may include Inter prediction direction,reference picture index, and motion vector.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of prediction structure for a scalablevideo coding system.

FIG. 2 illustrates a block diagram of an exemplary two-layer scalablevideo encoding system incorporating inter-layer Intra prediction.

FIG. 3 illustrates an example of up-sampling a base-layer texture blockand using the up-sampled base-layer block for prediction of anenhancement-layer block.

FIG. 4 illustrates an example of deriving multiple candidates for anenhancement-layer block based on motion information of a correspondingbase-layer block and neighboring blocks of the base-layer block.

FIG. 5 illustrates an exemplary flowchart of a scalable video codingsystem incorporating a transform type depending on transform unit sizeaccording to an embodiment of the present invention.

FIG. 6 illustrates an exemplary flowchart of a scalable video codingsystem incorporating derivation of multiple candidates to add to Mergeor AMVP candidate list for an enhancement-layer block based on motioninformation of a corresponding base-layer block and its neighboringblocks according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In H.264/AVC, only the discrete cosine transform (DCT) is used for theinter-layer texture prediction coded block. In HEVC, both the DCT andthe discrete sine transform (DST) can be used. Embodiments of thepresent invention apply a transform to the transform units of theenhancement layer video data processed by inter-layer textureprediction, where the transform type is dependent on the TU size. Forexample, if the TU size is equal to 4×4, the DST is applied. If the TUsize is larger than 4×4, the DCT is applied. The DCT and the DS arereferred as two different transform types in this disclosure. Othertransform types, such as Hadamard transform, may also be used topractice the present invention. The TU size-dependent transform can beapplied to coding units of the enhancement layer processed byinter-layer Intra prediction (ILIP, or so called inter-layer textureprediction) in scalable video coding. ILIP is used to remove the textureredundancy between layers. The reconstructed BL samples are up-sampledto generate the predictor for collocated EL (enhancement layer) samples,as shown in FIG. 2. The inter-layer prediction process comprisesidentifying the collocated block in the lower layer (e.g. BL) based onthe location of a corresponding EL block and interpolating thecollocated lower layer block to generate prediction samples for the ELas shown in FIG. 2. In scalable video coding, the interpolation processis used for inter-layer prediction by using predefined coefficients togenerate the prediction samples for the EL based on the lower layerpixels.

The example in FIG. 2 consists of two layers. However, an SVC system mayconsist of more than two layers. The BL picture is formed by applyingspatial decimation 210 to the input picture. The BL processing comprisesBL prediction 220. The BL input is predicted by BL prediction 220, wheresubtractor 222 is used to form the difference between the BL input dataand the BL prediction. The output of subtractor 222 corresponds to theBL prediction residues and the residues are processed bytransform/quantization (T/Q) 230 and entropy coding 270 to generatecompressed bitstream for the BL. Reconstructed BL data has to begenerated at the BL in order to form BL prediction. Accordingly, inversetransform/inverse quantization (IT/IQ) 240 is used to recover the BLresidues. The recovered BL residues and the BL prediction data arecombined using reconstruction 250 to form reconstructed BL data. Thereconstructed BL data is processed by in-loop filter 260 before it isstored in buffers inside the BL prediction. In the BL, BL prediction 220uses Inter/Intra prediction 221. The EL processing consists of similarprocessing modules as the BL processing. The EL processing comprises ELprediction 225, subtractor 228, T/Q 235, entropy coding 275, IT/IQ 245,reconstruction 255 and in-loop filter 265. However, the EL predictionalso utilizes reconstructed BL data as inter-layer prediction.Accordingly, EL prediction 225 comprises inter-layer prediction 227 inaddition to Inter/Intra prediction 226. The reconstructed BL data isinterpolated using up-sampling 212 and followed by inter-layer (IL)filtering 214 before it is used for inter-layer prediction. Thecompressed bitstreams from the BL and the EL are combined usingmultiplexer 280.

In FIG. 2, the encoder provides the difference information between theup-sampled BL and the EL in the enhancement bitstream. The differenceinformation is added to the prediction as inter-layer prediction. In theHEVC based scalable extension, when a coding unit (CU) in the EL iscoded as ILIP, the corresponding texture in the BL is up-sampled andused as texture predictors for the CU in the EL, as shown in FIG. 3.Block 310 corresponds to a 2N×2N reconstructed BL block. Block 312corresponds to an N×N sub-block of the 2N×2N reconstructed BL block.Block 312 is up-sampled to 2N×2N block 320. The up-sampled BL block(320) is then used for prediction of a collocated EL block (330). Thepredictors in block 331 are from other mode. The up-sampling procedureof generating the inter-layer texture prediction samples is based on theup-sampling filter and phase shift adopted in the HEVC standard. For themain coding profile of HEVC, DST is used for the Intra predictionresidue of the 4×4 coding unit (CU) of the luma component.

In the conventional scalable video coding (SVC) standard, bothinter-layer texture (Intra) prediction (ILIP) and Intra predictionwithin the same layer use the DCT. Embodiments of the present inventionselect the DST or DCT for luma inter-layer texture (Intra) predictionbased on the transform unit (TU) size. For example, if a CU is predictedby inter-layer texture (Intra) prediction and if the TU size is 4×4,then DST is used for the luma component and DCT is used for other TUsizes (i.e., TU size>4×4).

In another embodiment of the present invention, separable up-samplingfilters are used to up-sample the reconstructed BL signal forinter-layer prediction when DCT based up-sampling filter is used. Thesum of the filter coefficients is 128, i.e., 7 bit precision. Bothdirections (i.e., horizontal and vertical) use the same one-dimensional(1-D) DCT based up-sampling filter. An 8-tap 1-D DCT filter is used forthe luma component, and a 4-tap 1-D DCT filter is used for the chromacomponent. Depending on the up-sampling ratio, the locations ofup-sampled pixels are associated with different filter phases. A set offilter coefficients is used for pixels in each filter phase. The filtercoefficients are shown in Table 1 and Table 2. The phases ofdown-sampled sequences can be shifted according to the down-samplingmethod. Based on this, position and filter coefficients for up-samplingare determined by the phase of the down-sampled video sequence.

TABLE 1 Phase Filter coefficients 0 {0, 128, 0, 0}, 1/4 {−12, 112, 36,−8}, 1/3 {−13, 101, 50, −10}, 3/8 {−14, 96, 57, −11}, 1/2 {−13, 77, 77,−13},  7/12 {−12, 64, 90, −14}, 2/3 {−10, 50, 101, −13}, 7/8 {−4, 17,122, −7}, 11/12 {−3, 11, 125, −5}

TABLE 2 Phase Filter coefficients 0 {0, 0, 0, 128, 0, 0, 0, 0}, 1/3 {−3,9, −22, 105, 52, −18, 8, −3}, 1/2 {−3, 10, −23, 80, 80, −23, 10, −3},2/3 {−3, 8, −18, 52, 105, −22, 9, −3},

In HEVC, the motion information of neighboring block and temporalcollocated block can be used to derive the Merge and AMVP candidates.Advanced motion vector prediction (AMVP) is a coding tools used in HEVCfor Inter prediction. The motion information includes Inter predictiondirection (inter_pred_idc), reference index (refIdx), motion vector(MVs), motion vector predictor (MVP), MVP index, Merge index, Mergecandidate, etc. For scalable video coding extension of HEVC, the motioninformation of a corresponding block in BL can be utilized asinter-layer predictor or inter-layer candidate for EL motion informationprediction. For example, the scaled BL motion information can be addedinto the AMVP list and/or Merge list of the EL as one of the predictioncandidates. If the resolution of the EL block is two times of theresolution of the BL block, a motion vector for the BL block has to bescaled by a factor of two for the EL block.

The motion information of the corresponding block in the BL maycorrespond to the motion information within the corresponding block inthe BL. For example, the motion information associated with locationsa-h in the collocated block in BL as shown in FIG. 4 can be used toderive inter-layer prediction. In FIG. 4, block 410 corresponds to acurrent block in the EL and block 420 is the corresponding block in theBL. the motion information at a, b, g, and h in the BL are thecorresponding motion information of A, B, G, and H in EL. The c, d, e, fare the corresponding motion information of C, D, E, and F in the EL.Locations A, B, G, and H are the four corner pixels of the current blockin the EL and locations C, D, E, and F are the four center pixels of thecurrent block in the EL.

Not only the motion information of the corresponding block in the BL,but also the motion information of neighboring blocks of thecorresponding block in the BL can be utilized as inter-layer candidatesfor the EL to include in the Merge/AMVP candidate list. As shown in FIG.4, the neighboring candidates in BL, including t (bottom-right), a0(bottom-left), a1 (left), b0 (upper-right), b1 (top), and b2(upper-left) neighboring BL blocks, can be used as a candidate for theEL to include in the Merge/AMVP candidate derivation. The collocated ELneighboring blocks correspond to T (bottom-right), A0 (bottom-left), A1(left), B0 (upper-right), B1 (top), and B2 (upper-left) neighboring ELblocks respectively.

In H.264/AVC, only one inter-layer candidate is used for MV prediction.Embodiments of the present invention use two or more inter-layercandidates for the EL to include in the Merge/AMVP candidate derivation.The inter-layer candidates can be the motion information inside thecorresponding block in BL (e.g. motion information associated with a-hin FIG. 4) or the motion information of the neighboring bocks of thecorresponding block in BL (e.g. the a0, a1, a2, b0, b1, b2 and t in FIG.4). For example, two inter-layer candidates for the EL to include in theMerge candidate list or the AMVP candidate list can be used, where onecandidate corresponds to location c and the other candidate correspondsto location tin FIG. 4. In another example, one candidate corresponds tolocation f and the other candidate corresponds to location h in FIG. 4.To reduce the candidate redundancy, the latter inter-layer candidatescan perform the redundancy check with the first inter-layer candidate orany EL candidates.

FIG. 5 illustrates an exemplary flowchart of a scalable video codingsystem incorporating an adaptive transform type selection based ontransform unit size according to an embodiment of the present invention.The video data is configured into a Base Layer (BL) and an EnhancementLayer (EL), where the EL video data has higher spatial resolution orbetter video quality than the BL video data. The system receives inputdata associated with the EL video data, wherein the EL video data ispartitioned into TUs (transform units) having a TU (transform unit) sizeas shown in step 510. For encoding, the input data corresponds to theinter-layer prediction processed video data that is to be coded. Fordecoding, the input data corresponds to coded inter-layer predictionprocessed video data that is to be decoded. The input data may beretrieved from storage such as a computer memory, buffer (RAM or DRAM)or other media. The input data may also be received from a processorsuch as a controller, a central processing unit, a digital signalprocessor or electronic circuits that produce the input data. A firsttype transform/inverse transform or a second type transform/inversetransform is applied to the input data corresponding to a current TU ofthe EL video data depending on a current TU size as shown in step 520.

FIG. 6 illustrates an exemplary flowchart of a scalable video codingsystem incorporating motion candidate derivation for the enhancementlayer based on motion information in the base layer according to anembodiment of the present invention. The system receives input dataassociated with a current EL block of the EL video data as shown in step610 and determines a corresponding BL block in the BL as shown in step620. Two or more inter-layer candidates are derived based on BL motioninformation associated with corresponding BL video data as shown in step630, wherein said two or more inter-layer candidates are added to Mergecandidate list or AMVP (advanced motion vector prediction) candidatelist, and wherein the corresponding BL video data includes thecorresponding BL block. A final motion vector predictor is derived fromthe Merge candidate list or the AMVP candidate list as shown in step640. Encoding or decoding is then applied to the input data associatedwith the current EL block using the final motion vector predictor,wherein the current EL block is coded in Merge mode or Inter mode basedon AMVP as shown in step 650.

The flowchart shown above is intended to illustrate an example ofscalable video coding. A person skilled in the art may modify each step,re-arranges the steps, split a step, or combine steps to practice thepresent invention without departing from the spirit of the presentinvention.

The above description is presented to enable a person of ordinary skillin the art to practice the present invention as provided in the contextof a particular application and its requirement. Various modificationsto the described embodiments will be apparent to those with skill in theart, and the general principles defined herein may be applied to otherembodiments. Therefore, the present invention is not intended to belimited to the particular embodiments shown and described, but is to beaccorded the widest scope consistent with the principles and novelfeatures herein disclosed. In the above detailed description, variousspecific details are illustrated in order to provide a thoroughunderstanding of the present invention. Nevertheless, it will beunderstood by those skilled in the art that the present invention may bepracticed.

Embodiment of the present invention as described above may beimplemented in various hardware, software codes, or a combination ofboth. For example, an embodiment of the present invention can be acircuit integrated into a video compression chip or program codeintegrated into video compression software to perform the processingdescribed herein. An embodiment of the present invention may also beprogram code to be executed on a Digital Signal Processor (DSP) toperform the processing described herein. The invention may also involvea number of functions to be performed by a computer processor, a digitalsignal processor, a microprocessor, or field programmable gate array(FPGA). These processors can be configured to perform particular tasksaccording to the invention, by executing machine-readable software codeor firmware code that defines the particular methods embodied by theinvention. The software code or firmware code may be developed indifferent programming languages and different formats or styles. Thesoftware code may also be compiled for different target platforms.However, different code formats, styles and languages of software codesand other means of configuring code to perform the tasks in accordancewith the invention will not depart from the spirit and scope of theinvention.

The invention may be embodied in other specific forms without departingfrom its spirit or essential characteristics. The described examples areto be considered in all respects only as illustrative and notrestrictive. The scope of the invention is therefore, indicated by theappended claims rather than by the foregoing description. All changeswhich come within the meaning and range of equivalency of the claims areto be embraced within their scope.

The invention claimed is:
 1. A method of inter-layer prediction forscalable video coding, wherein video data is configured into a BaseLayer (BL) and an Enhancement Layer (EL) and wherein EL video data hashigher spatial resolution or better video quality than BL video data,the method comprising: receiving input data associated with a current ELblock of the EL video data; determining a corresponding BL block in theBL, wherein four corner BL pixels and four center BL pixels arecollocated with four corner EL pixels and four center EL pixels of thecurrent EL block respectively; deriving two or more inter-layercandidates based on BL motion information associated with correspondingBL video data, wherein: a first inter-layer candidate of the two or moreinter-layer candidates corresponds to motion information associated withone of the four corner BL pixels; a second inter-layer candidate of thetwo or more inter-layer candidates corresponds to motion informationassociated with one of the four center BL pixels; and said two or moreinter-layer candidates are added to Merge candidate list or AMVP(advanced motion vector prediction) candidate list; deriving a finalmotion vector predictor from the Merge candidate list or the AMVPcandidate list; and applying encoding or decoding to the input dataassociated with the current EL block using the final motion vectorpredictor, wherein the current EL block is coded in Merge mode or Intermode based on AMVP.
 2. The method of claim 1, wherein at least one ofsaid two or more inter-layer candidates is derived based on scaled BLmotion information associated with selected BL video data in thecorresponding BL block.
 3. The method of claim 2, wherein the selectedBL video data in the corresponding BL block corresponds to at least onelocation of the four corner BL pixels and the four center BL pixels. 4.The method of claim 1, wherein at least one of said two or moreinter-layer candidates is derived based on second scaled BL motioninformation associated with one or more neighboring BL blocks of thecorresponding BL block.
 5. The method of claim 4, wherein said one ormore neighboring BL blocks of the corresponding BL block correspond to abottom-left BL block, a left BL block, an upper-right BL block, a top BLblock and an upper-left BL block, wherein the bottom-left BL block, theleft BL block, the upper-right BL block, the top BL block and theupper-left BL block correspond to collocated bottom-left EL block, leftEL block, upper-right EL block, top EL block and upper-left EL block ofthe current EL block respectively.
 6. The method of claim 1, wherein theBL motion information includes Inter prediction direction, referencepicture index, and motion vector.
 7. The method of claim 1, wherein asecond inter-layer candidate of said two or more inter-layer candidatesis checked for redundancy against a first inter-layer candidate of saidtwo or more inter-layer candidates, wherein the second inter-layercandidate of said two or more inter-layer candidates is derived afterthe first inter-layer candidate of said two or more inter-layercandidates.
 8. An apparatus for inter-layer prediction for scalablevideo coding, wherein video data is configured into a Base Layer (BL)and an Enhancement Layer (EL) and wherein EL video data has higherspatial resolution or better video quality than BL video data, theapparatus comprising: processing circuitry configured to: receive inputdata associated with a current EL block of the EL video data; determinea corresponding BL block in the BL, wherein four corner BL pixels andfour center BL pixels are collocated with four corner EL pixels and fourcenter EL pixels of the current EL block respectively; derive two ormore inter-layer candidates based on BL motion information associatedwith corresponding BL video data, wherein: a first inter-layer candidateof the two or more inter-layer candidates corresponds to motioninformation associated with one of the four corner BL pixels; a secondinter-layer candidate of the two or more inter-layer candidatescorresponds to motion information associated with one of the four centerBL pixels; and said two or more inter-layer candidates are added toMerge candidate list or AMVP (advanced motion vector prediction)candidate list; derive a final motion vector predictor from the Mergecandidate list or the AMVP candidate list; and apply encoding ordecoding to the input data associated with the current EL block usingthe final motion vector predictor, wherein the current EL block is codedin Merge mode or Inter mode based on AMVP.